Transmit and receive isolation for ultrasound scanning and methods of use

Abstract

Methods and systems for isolating transmit and receive circuitry at an ultrasound transducer element are provided. Separate electrodes or electrodes on opposite sides of a transducer element are connected to the separate transmit and receive paths or channels. Instead of high voltage transmit and receive switching, the transducer element isolates the transmit channel from the receive channel. The transmit channel includes circuitry for limiting the voltage at one electrode during receive processing, such as a switch operable to connect the electrode to ground. The receive channel includes circuitry for limiting the voltage at an electrode during transmit processing, such as a diode clamp preventing voltage swings greater than diode voltage at the electrode. Limiting the voltage provides virtual grounding or a direct current for either of the transmit or receive operation. Using a transmit channel discussed above or other transmit channels, a unipolar pulse may be generated starting at one voltage and ending at a different voltage. For example, a unipolar pulse is generated starting at a zero voltage value and ending on a positive voltage value. A subsequent unipolar pulse is transmitted by starting at the positive voltage value and ending on the zero voltage value. These mirrored unipolar transmit waveforms may be used for phase inversion imaging, such as adding responsive received signals for isolating harmonic information.

What is claimed is:  
     
       1. A system for transmit and receive isolation for ultrasound processing, the system comprising: 
       a transducer element having first and second electrodes;  
       a transmit path connected to the first electrode; and  
       a receive path connected to the second electrode, the receive path separate from the transmit path at the transducer element.  
     
     
       2. The system of  claim 1  wherein the transmit path comprises a waveform generator, the waveform drive circuit positioned in a probe, the transducer element also positioned in the probe, and further comprising: 
       a cable connectable between the probe and a base unit.  
     
     
       3. The system of  claim 1  wherein the receive path comprises at least one amplifier and a filter, the at least one amplifier and filter positioned in a probe, the transducer element also positioned in the probe, and further comprising: 
       a cable connectable between the probe and a base unit.  
     
     
       4. The system of  claim 1  wherein the transmit path comprises a waveform generator and the receive path comprises a time gain control circuit, the waveform generator, time gain control circuit and transducer element in a probe, the probe separate from an imaging base unit. 
     
     
       5. The system of  claim 1  wherein the receive path comprises a multiplexer. 
     
     
       6. The system of  claim 1  wherein the receive path comprises at least two diodes electrically connected with the second electrode. 
     
     
       7. The system of  claim 6  wherein the at least two diodes electrically connect between the second electrode and a ground, the two diodes comprising a diode clamp. 
     
     
       8. The system of  claim 1  further comprising a plurality of additional transducer elements, the transducer element and additional transducer elements arranged in an N×M grid where N and M are both greater than one. 
     
     
       9. The system of  claim 1  wherein the transmit path comprises at least one transistor electrically connectable between the first electrode and a reference potential. 
     
     
       10. The system of  claim 1  wherein the transmit path is operable to connect the first electrode to ground during receive operation of the transducer element and the receive path is operable to limit a voltage on the second electrode during transmit operation of the transducer element. 
     
     
       11. The system of  claim 1  wherein the transmit path includes at least one high voltage component and the receive path is free of high voltage components. 
     
     
       12. The system of  claim 1  wherein the transmit and receive paths are free of any switch operable to select between the transmit path and the receive path. 
     
     
       13. The system of  claim 1  wherein all electrodes of the transducer element are free of a direct connection to ground. 
     
     
       14. A method for ultrasound isolation of transmit and receive events, the method comprising: 
       (a) applying a transmit waveform to a first electrode of a transducer element;  
       (b) limiting the voltage at a second electrode during (a);  
       (c) receiving electrical signals on the second electrode of the transducer element, the second electrode different than the first electrode; and  
       (d) limiting the voltage at the first electrode during (c).  
     
     
       15. The method of  claim 14  further comprising: 
       (e) generating the transmit waveform in a probe where the transducer element is also in the probe.  
     
     
       16. The method of  claim 14  further comprising: 
       (e) filtering the electrical signals with a filter, the filter in a probe wherein the transducer element is also in the probe.  
     
     
       17. The method of  claim 14  wherein (a) comprises driving the transducer element with driver circuits in a probe separate from an imaging base unit, the probe including the transducer element, and further comprising: 
       (e) adjusting gain of the electrical signals as a function of time with a time gain control circuit, the time gain control circuit in the probe.  
     
     
       18. The method of  claim 14  further comprising: 
       (e) multiplexing the electrical signals with signals responsive to different transducer elements.  
     
     
       19. The method of  claim 14  wherein (d) comprises clamping the second electrode with at least two diodes electrically connected with the second electrode. 
     
     
       20. The method of  claim 14  wherein (b) comprises electrically connecting the first electrode with a reference potential. 
     
     
       21. The method of  claim 14  further comprising: 
       (e) performing (a)-(d) for a plurality of transducer elements arranged as a two-dimensional array.  
     
     
       22. The method of  claim 14  wherein (a) and (d) are performed with at least one high voltage component and (b) and (c) are performed free of high voltage components. 
     
     
       23. The method of  claim 14  wherein (a)-(d) are performed free of selecting between a transmit path and a receive path. 
     
     
       24. The method of  claim 14  wherein (a) comprises applying a unipolar waveform, a beginning of the unipolar waveform being a first state and the ending of the unipolar waveform being a second state different than the first state, the first and second states comprising different ones of a high state and a low state. 
     
     
       25. A method for transmitting acoustic energy with phase inversion, the method comprising: 
       (a) generating a first unipolar transmit waveform having a high state and a low state;  
       (b) generating a second unipolar transmit waveform having the high state and the low state;  
       (c) beginning the first unipolar transmit waveform in the low state; and  
       (d) beginning the second unipolar transmit waveform in the high state.  
     
     
       26. The method of  claim 25  further comprising: 
       (e) ending the first unipolar transmit waveform in the high state; and  
       (f) ending the second unipolar transmit waveform in the low state.  
     
     
       27. The method of  claim 25  wherein (a)-(d) comprise generating the first and second unipolar transmit waveforms such that a sum of the transmit waveforms as applied to a transducer element is substantially zero. 
     
     
       28. The method of  claim 25  wherein (c) comprises beginning the first unipolar transmit waveform at a zero voltage and (d) comprises beginning the second unipolar transmit waveform at a positive voltage.